DUAL OUTPUT MULTI FUNCTION INTERFACE DEVICE FOR AUDIO SYSTEMS

Abstract: A multifunction amplifier device for matching an audio signal from an audio signal source, such as a video game, stereo or movie, to a pre-determined frequency of a transducer is disclosed. The amplifier device includes a low pass filter coupled to the audio signal source for developing a filtered signal from the audio signal. A frequency dividing circuit is coupled to the low pass filter for dividing the frequencies of the filtered signal by a pre-determined factor. The amplifier device futher includes a decoding circuit coupled to said low pass filter for selecting between a left and a right audio channel of the filtered signal and developing a decoded signal and a muting circuit coupled to the decoding circuit. The muting circuit only passes the decoded signal at levels above a variable threshold level. A power amplifier is coupled to the frequency dividing circuit and the muting circuit for amplifying the audio signal into an amplified signal having a frequency level corresponding to the pre-determined frequency of the transducer.

Description: DUAL OUTPUT MULTI FUNCTION INTERFACE DEVICE FOR AUDIO SYSTEMS FIELD OF THE INVENTION The present invention relates generally to an interface device, and more particularly to a dual output, multi-function amplifier for interfacing the audio signal of a video game with a transducer for imparting vibratory motion to the video game player in response to the audio signals. BACKGROUND OF THE INVENTION The popularity of electronic video games has created an increasing demand for features that allow the player to interact with the video game and for the game to become more realistic. For example, the recent developments in video game software technology provide more vivid video images and more realistic sounds for the video game. Other developments in the video game marketplace include virtual reality games and laser disk games. In virtual reality games, the player is surrounded by holograms so that the player feels they are a physical element in the game. In laser disk games, the player has a clear and realistic video image for the game. Both virtual reality and laser disk games allow the player to feel that they are more actively participating in the video game. One obvious drawback of the new developments such as virtual reality and laser disks is their cost. The virtual reality and laser disk systems require a computer or laser disk player. Although the typical video game player is attracted to the unique features of virtual reality, the typical video player does not want to invest in a new computer system or laser disk player, having already invested in their video game setup, such as the popular SEGA (TM) or NINTENDO (TM) video games. Moreover, video game players have typically invested in video game software that is unique to their video game system. Therefore, a need exists for an interactive video game accessory system that (1) enables the video game player to enjoy interactive features with the video game, (2) is low cost, and (3) can easily interface with existing video game systems. One example of such an interactive feature is the use of a transducer, such as the one described in commonly owned U.S. Patent Application No. 08/086,622, which is incorporated herein by reference, to impart vibratory sensations to the video game player as the player operates the game. The vibratory sensations produced by the transducer correspond to the audio track of the video game. The transducer may be placed in a seat cushion or, as shown in Figure 1 of the present application, in a vest that is worn by the video game player. The transducer therefore is in contact with the video game player, and enables the video game player to "feel" the audio track of the game. Although it is desirable to provide these remote interaction devices for the video game, it is not possible to simply couple a transducer, such as the type described in U.S. Patent Application No. 08/086,622, to the audio output of the video game because the frequency at which the transducer optimally operates is not matched to the frequency of the audio signal from the video game. As described in U.S. Patent Application No. 08/086,622, in the transducer, an alternating current is applied to cause the transducer to vibrate. The frequency of the vibration will be centered about a natural frequency as determined by the mass of one assembly of the transducer and the combined spring constants of two flexures. The natural frequency is tuned to the base of the audio spectrum of the video game to enhance the sound quality of the base by imparting low frequency vibrations through an article containing the transducer with which the player is in direct contact. The audio signal, however, includes both high and low level frequencies, as compared to the transducer that operates at low frequencies. Therefore, if the audio signal source was directly coupled to the transducer, the transducer would "buzz" due to the high frequencies in the audio signal. An interface device is therefore necessary to interface the video game audio output with the transducer to prevent the transducer from "buzzing". A signal stronger than the audio signal is also required in order to drive the transducer. Therefore, it is necessary to amplify the signal to the level required by the transducer. The amplified signal must also match the impedance of the transducer in order to avoid damaging the amplifier. It is also desirable to have a video game accessory that easily connects to the video game. The easier it is to connect the interactive video game accessory to the video game, the more likely the system will be used by the video game player. As previously described, the transducer may be used within an interactive audio system in connection with the audio sound track from a video game, music, television, movie, or computer soundboard. Depending on which audio source is selected, the user may desire to "feel" different types of sounds through the transducer. For example, if the transducer is used in connection with a video game, the user will probably prefer to feel the full force of the punches, kicks and explosions that occur during the course of the game. The player may further want to block out the lower level background sounds as they may distract from the action of the game. Alternatively, if the transducer is used in connection with stereo music, the user will probably prefer to feel a natural fidelity sound and will not want to block out the lower level sounds. Therefore, it is desirable to have an interfacing amplifier that provides additional functions, such as filtering lower level sounds and/or changing the frequency of the audio signal to feel the full force of the sound. These additional amplifier functions will enable one interactive audio system to accommodate a variety of soundtracks, while still providing the user with the desired vibrations and sensations for each type of soundtrack. As previously stated, the user may desire to eliminate or reduce the background audio noise in order to increase the impact of certain audio signals, such as the kicks, punches or explosions in video games. Therefore a need exists for a method of gating specific audio segments of a soundtrack. If the interactive audio system is used in connection with a video game, two competing video game players may both wish to feel the impact and vibrations from the transducer. Therefore, it also desirable to have dual output amplifier that allows the amplifier to be interconnected with two separate transducers. SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to overcome one or more disadvantages and limitations of the prior art. A significant object of the present invention is to provide a interface device for safely interfacing the audio signal of a video game with a transducer. Another object of the present invention is to provide an interactive video game system that allows the video game player to feel the vibrations from the audio signal of a video game. A significant object of the present invention is to provide a dual output interface amplifier device that allows an audio source to be coupled with two separate transducers. Another object of the present invention is to provide a multi-function amplifier for interfacing an audio source with a transducer that only allows certain audio segments to be passed to the transducer. According to a broad aspect of the present invention, a multifunction amplifier device for matching an audio signal from an audio signal source, such as a video game, stereo or movie, to a pre-determined frequency of a transducer includes a low pass filter coupled to the audio signal source for developing a filtered signal from the audio signal. A frequency dividing circuit is coupled to the low pass filter for dividing the frequencies of the filtered signal by a pre-determined factor. The amplifier device further includes a decoding circuit coupled to said low pass filter for selecting between a left and a right audio channel of the filtered signal and developing a decoded signal and a muting circuit coupled to the decoding circuit The muting circuit only passes the decoded signal at levels above a variable threshold level. A power amplifier is coupled to the frequency dividing circuit and the muting circuit for amplifying the audio signal into an amplified signal having a frequency level corresponding to the pre-determined frequency of the transducer. A feature of the present invention is that the interface device allows for easy and quick interconnection of the transducer to the video game. A further feature of the present invention is that the interface device allows for amplification of the low frequency audio signal required to drive a transducer. A feature of the present invention is that the amplifier device includes dual outputs that accommodates for two users of the interactive audio system. A further feature of the present invention is that the amplifier device allows the user to only feel certain selected audio signals, and not feel undesired background audio signals. These and other objects, advantages and features of the present invention will become readily apparent to those skilled in the art from a study of the following description of an exemplary preferred embodiment when read in conjunction with the attached drawing and appended claims. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a representative view of the interactive audio system according to the principles of the present invention; Figure 2 is a block diagram of a first embodiment of the interface device according to the principles of the present invention; and Figure 3 is an electrical schematic of the first embodiment of the interface device according to the principles of the present invention. Figure 4 is a block diagram of a second embodiment of the interface device according to the principles of the present invention; and Figure 5 is an electrical schematic of the second embodiment of the interface device according to the principles of the present invention. DESCRIPTION OF AN EXEMPLARY PREFERRED EMBODIMENT Referring now to Figure 1 , a diagram of the interactive audio system 10 of the present invention is shown. The interactive system 10 includes a transducer 12 enclosed in a cushion 14, vest, or other article of clothing, an interface amplifier device 16, and an audio signal source 18. As shown in Figure 1 , the audio signal source 18 may include, but is not limited to, an existing video game system, such as a SEGA (TM) video game system 18(a) or an NINTENDO (TM) video game system 18(b), a CD player 18(c), or a portable stereo 18(d). The transducer 12 is contained in the cushion or vest 14 in order to enable the video game player to "feel" the vibrations of audio signals. Alternatively, the transducer may be contained in another type of article of clothing, or secured to a piece of furniture with which the video game player will have contact. The cushion or vest 14 is designed to allow a preferably 90 degree right angle 1/8 inch mini stereo plug 20 to be plugged into the vest or cushion 14. The mini stereo plug 20 is coupled to a first stereo head phone cord 22. The first head phone cord 22 is preferably eighteen gauge and approximately one foot in length. The first stereo head phone cord 22 is coupled to a four position slide switch 24. The slide switch 24 is designed to handle two amps at forty volts AC, and includes two resistors, a first resistor at four to five ohms and a minimum of five watts, and a second resistor at eight to ten ohms and a minimum of two watts. The slide switch 24 is coupled to a second stereo head phone cord 26. The second head phone cord 26 is preferably eighteen gauge cord and approximately twenty feet in length. The second head phone cord 26 is also preferably coiled to avoid tangling of the cord during use and storage. The second head phone cord 26 is coupled to a one-eighth inch mini stereo plug 28, which is plugged into a housing 32 enclosing the interface device 16. The second head phone cord 26 may alternatively be coupled to a multi mini stereo plug attachment 29, to allow the interface device 16 to be coupled to a plurality of transducers 12. The interface device housing 32 therefore includes a one-eighth inch female mini plug 30 that is chassis mounted to housing 32 of the interface device 16. The interface device housing 32 further includes a left and a right female RCA plug 34 (a) (b), which are also chassis mounted on the housing 32. Each of the video games 18 (a) (b), the CD player 18(c) and the portable stereo 18(d) includes a third cord 36 for coupling the game or stereo audio output on a first end 38 of the cord 36 to the interface device 16 on the opposite end 40 of the cord 36. As shown in Figure 1 , the SEGA (TM) video game 18(a) preferably utilizes the third cord 36(a) with an A/V DIN plug 42 on the first end 38(a) for interconnection to the video game, and an RCA male plug 44 on the opposite end 40(a) for interconnection with the interface device. The NINTENDO (TM) video game 18(b) preferably utilizes the third cord 36(b) having a NINTENDO (TM) A/V plug 46 on the first end 38(b) to interconnect to the video game, and two RCA male plugs 48 on the opposite end 40(b) for interconnection with the interface device. The CD player 18(c) uses the third cord 36(c) with two RCA male plugs 50 on the first and opposite ends 38(c), 40(c) to interconnect with both the CD player and the interface device. The portable stereo 18(d) preferably uses the third cord 36(d) with one one-eighth inch mini plug 52 on the first end 38(d) to connect to the stereo, and two RCA male plugs 54 on the opposite end 40(d) for interconnection with the interface device. The CD and portable stereo may further require splitters (not shown), as commonly known in the art, to enable both the transducer and speakers or headphones to be coupled to the audio output. Referring now to Figures 2 and 3, the interface device 16 of the first embodiment of the present invention is explained in detail. In Figure 2, a block diagram of the first embodiment of the interface device 16 is shown. The interface device 16 includes a power supply 56, a low pass filter 58, and an amplifier 60. The interface device 16 is used to interface the input signal from the audio signal source 18 with the transducer 12. The low pass filter 58 and amplifier 60 are preferably enclosed in the housing 32, as described hereinabove with reference to Figure 1 for convenience to the user. The housing includes several chassis mounted female plugs 30,34 to allow quick connections of the interface device 16 to the audio signal source 18 and transducer 12. In the embodiment shown in Figures 2 and 3, the input signal is derived from the audio signal source 18 as shown in Figure 1. The transducer 12 is an electromagnetic transducer, similar to the transducer described in co-pending U.S. Patent Application No. 08/086,622. It is to be understood however that other sources of input audio signals, and other transducers may be utilized with the interface device. In the interface device 16, the input signal is an audio signal of approximately 50 mv. The audio game signal is applied to the low pass filter 58 with a preferably 100 hertz cutoff frequency to attenuate the frequencies of the audio signal above the approximately 100 hertz range. The filter 58 further introduces a gain in the signal of two times. The low pass filter 58 therefore produces a filtered signal at approximately 100 mv. The filtered signal is then applied to a power amplifier 60, which amplifies the signal approximately one hundred times to produce an amplified signal at approximately ten volts. The amplified signal is then used to drive the transducer 12, which preferably operates at approximately twenty watts and four ohms. The interface device 16 further includes a twelve volt AC power supply 56 that is coupled to both the low pass filter 58 and the power amplifier 60. The power supply 56 is preferably wall mountable, and preferably includes a step down transformer 62 for stepping down a 120 Volt source to twelve volts AC. A basic block diagram of the second embodiment of the interactive audio system 70 is shown in Figure 4. The system includes the audio signal source 18, a multifunction amplifier interface device 68, the transducer 12 and the power supply 56. The audio input signal is received from the audio signal source and applied to the input filter circuit 72 of the multi-function amplifier. The input filter circuit 72 is coupled to both the frequency dividing circuit 74, the A/B decoding circuit 76 and the muting or threshold signal level circuit 78. The A/B decoding circuit allows the user to select either a right audio channel, a left audio channel, or both channels. The frequency divider circuit serves to divide the frequency of the signal by a pre-determined factor to produce a lower frequency signal that is more fully sensed by the user. The muting circuit 78 serves to enable the user to filter the lower signal levels, such as background music. Both the frequency divider circuit and the muting circuit are coupled to the power amplifier 80. The power amplifier is coupled to the transducer and amplifies the signal to a level necessary to operate the transducer. Each of these circuits in the multi-function amplifier is now described in detail with reference to Figure 5. As shown in Figure 5, the audio input signal is first applied from either mono or stereo inputs at input 82 to a volume control circuit that is controlled a volume control circuit potentiometer 88. The potentiometer 88 allows the user of the interactive audio system to control the volume of the audio signal directed to the transducer. Stereo inputs present at input 82 are mixed by resisitors 84 and 86 The input signal is then applied to a gain stage and low pass filter to attenuate the frequencies of the audio signal above either a preset or a variable cut-off frequency. In the embodiment shown in Figure 5, the low pass filter has a 400 hertz corner frequency and rolls off at approximately 15 dB per octave., however, other cut-off frequencies may apply. The gain stage and low pass filter produces a filtered signal, which is applied to the A/B decoding circuit, the frequency divider circuit and the muting circuit. The A/B decoding circuit 76 includes. a comparator 87, a unity gain amplifier 90, and an A/B switch 92. The comparator 87 forms a differentiator with a high frequency rolloff to eliminate unwanted noise. A/B switch 92 is used to select either the right audio channel, the left audio channel, or both channels. The decoded signals generated by the A/B decoding circuit are used by the muting circuit to gate the audio output stage. The A/B decoding circuit therefore allows the interactive audio system of the present invention to accommodate two users, one on each of the left and the right audio channels. As previously described, the muting circuit allows the user to filter out lower level input signals, such as background music, below a threshold signal level. The muting circuit monitors the level of the filtered signal, and filters out the signal levels above a preset or variable threshold signal level. As shown in Figure 5, the muting circuit includes a muting comparator 94 and a muting potentiometer 96 for varying the threshold signal level. The muting circuit compares the rectified filtered input amplitude against the threshold voltage set by the potentiometer 96. When the input exceeds the threshold level, the muting circuit sends an output signal to the analog switch 98 to enable the analog switch. In order to enhance the vibrations and impacts felt from certain audio signal, it may be desirable to gate those certain audio signals. In order for the amplifier to detect a segment of audio that is to be gated, the audio segment requires an initial detectable pulse at the beginning of the audio segment. The initial detectable pulse is followed by a series of sustaining pulses for the duration of the gated segment. Assuming the D/A output is +/- 1 , each transition occurs in one sample time. The initial detectable pulse begins at zero, with the next sustaining pulse decreasing to -.75; the following sustaining pulse increases to +.75; and the following sustaining pulse decreases to zero. The audio signal remains gated for 70 msec, after the last sustaining pulse is detected. To insure reliability of the gating, the initial detectable pulse is isolated from the signals, although signals of a low amplitude may be merged directly with the initial detectable pulse. Pulse shapes for the initial detectable pulse and the sustaining pulses are computer generated for any desired gating length. The user can then merge the computer generated pulses into the desired audio signal. As previously described, the frequency divider circuit divides the frequencies of the filtered signal by a preset factor. Because the user can better perceive the signals at lower frequencies, the frequency divider circuit allows the user to feel the full force of the audio soundtrack. The frequency divider circuit includes a MUSIC/GAME or ON/OFF switch 100. If the interactive audio system is used in connection with a video game, the user may desire the "GAME" or "ON" position to feel the full force of the punches kicks and explosions of the game. However, if the interactive audio system is used in connection with a stereo or movie, the user may prefer the "MUSIC" or "OFF" position in order to enjoy the feel of a more realistic and natural sound. Therefore, the frequency divider circuit provides the user of the interactive audio system with two options from which to choose depending on their own personal preference; a full force type of sensation or a natural fidelity type of sensation. In the embodiment shown in Figure 5, the frequency divider circuit divides the input frequency content by switching between inverting and non-inverting half waves. Both inverted and non- inverted waves are sent to the inputs of the analog switch 98. The analog switch is controlled by a counter formed by flip flop 102 which is clocked by a zero crossing detector formed by comparator 204. The multi-function amplifier 68 may also include the clipping indicator circuit 106 with a corresponding clipping indicator LED 108. A clipping circuit comparator 1 10 compares the rectified filtered input signal against a preset voltage. When the amplitude of the input signal exceeds the preset voltage the output of the muting comparator 94 turns on the clipping indicator LED 108. The power amplifier 80 amplifies the signals received from the analog switch 98 to produce an amplified signal that is then used to drive the transducer 12, which preferably operates at approximately eighteen watts RMS and four ohms. There has been described hereinabove an exemplary preferred embodiment of the interface device according to the principles of the present invention. Those skilled in the art may now make numerous uses of, and departures from, the above- described embodiments without departing from the inventive concepts disclosed herein. Accordingly, the present invention is to be defined solely by the scope of the following claims.

Claims: THE CLAIMS I claim as my invention: 1. An interfacing system for matching an audio signal from an audio signal source to a pre-determined frequency of a load comprising: at least one transducer, said transducer operating at the pre-determined frequency; a low pass filter coupled to the audio signal source for developing a filtered signal from said audio signal; and an amplifier coupled to said filter and said transducer for amplifying said filtered signal into an amplified filtered signal sufficient to drive said transducer, said amplified filtered signal having a frequency level corresponding to the pre- determined frequency of the transducer. 2. An interfacing system in accordance with Claim 1 further comprising an article of clothing, wherein said transducer is contained within the article of clothing. 3. An interfacing system in accordance with Claim 1 further comprising a cushion, wherein said transducer is contained within the cushion. 4. An interfacing system in accordance with Claim 1 further comprising a piece of furniture, wherein said transducer is secured to said piece of furniture. 5. An interfacing system in accordance with Claim 1 wherein said interface device further comprises a power supply, said power supply coupled to both said filter and said amplifier. ' 6. An interfacing system in accordance with Claim 1 wherein said filter has a cut-off frequency selected to attenuate high frequency noise above 100 hertz. 7. An interfacing system in accordance with Claim 5 wherein said power supply is comprised of a stepdown transformer, said transformer stepping down a 120 volt source to twelve volts AC. 8. An interfacing system in accordance with Claim 1 further comprising a housing, said housing enclosing said filter and amplifier. 9. An interfacing system in accordance with Claim 8 wherein said housing further includes a first female plug for coupling said interface box to the transducer. 10. An interfacing system in accordance with Claim 8 wherein said housing further includes a second and third female plug for coupling said interface box to the audio signal source. 1 1 . An interactive system for an audio signal source generating an audio signal comprising: at least one transducer for receiving the audio signal and generating a vibratory motion in response to the audio signal, said transducer operating at a pre-determined frequency; and an interface device, said interface device coupled to said video game and said transducer and comprising a low pass filter for receiving the audio signal and passing a filtered signal having a frequency corresponding to the pre-determined frequency of the audio signal and an amplifier coupled to said filter for receiving and amplifying the filtered signal to a level sufficient to drive the transducer. 12. An interactive system in accordance with Claim 1 1 further comprising an article of clothing, wherein said transducer is contained within the article of clothing. 13. An interactive system in accordance with Claim 11 further comprising a cushion, wherein said transducer is contained within the cushion. 14. An interactive system in accordance with Claim 11 further comprising a piece of furniture, wherein said transducer is secured to said piece of furniture. 15. An interactive system in accordance with Claim 1 1 wherein said filter has a cut-off frequency selected to attenuate high frequency noise above 100 hertz. 1 6 An interactive system in accordance with Claim 15 wherein said power supply is comprised of a stepdown transformer, said transformer stepping down a 120 volt source to twelve volts AC. 17. An interactive system in accordance with Claim 1 1 further comprising a frequency dividing circuit coupled to said low pass filter and said amplifier, said frequency dividing circuit dividing the frequencies of the filtered signal by a pre- determined factor, developing a frequency divided signal, and applying the frequency divided signal to said amplifier. 18. An interactive system in accordance with Claim 11 wherein said amplifier device further comprises a threshold signal level circuit coupled to said low pass filter, said threshold signal level circuit having a threshold signal level and only passing the filtered signal at levels above said threshold level. 19. An interactive system in accordance with Claim 18 wherein said threshold signal level is variable. 1 20. An interactive system in accordance with Claim 18 further comprising a decoding circuit coupled to said low pass filter and said threshold signal level circuit for selecting between a left and a right audio channel of said filtered signal and developing a decoded signal, and applying said decoded signal to said threshold signal level circuit. 1 21 . An amplifier device for matching an audio signal from an audio signal source to a pre-determined frequency of a load comprising: a low pass filter coupled to the audio signal source for developing a filtered signal from said audio signal; 6 a frequency dividing circuit coupled to said low pass 7 filter, said frequency dividing circuit dividing the frequencies of 8 the filtered signal by a pre-determined factor and developing a 9 frequency divided signal; and o an amplifier coupled to said frequency dividing circuit i and the load for amplifying the frequency divided signal into an 2 amplified signal having a frequency level corresponding to the 3 pre-determined frequency of the load. ι 22. An amplifier device in accordance with Claim 21 2 further comprising a threshold signal level circuit coupled to said 3 low pass filter, said threshold signal level circuit having a 4 threshold signal level and only passing the filtered signal at 5 levels above said threshold level. ι 23. An amplifier device in accordance with Claim 21 2 wherein said frequency dividing circuit comprises at least one 3 flip-flop. 1 24. An amplifier device in accordance with Claim 23 2 wherein said frequency dividing circuit comprises two flip-flops, 3 and the pre-determined factor is four. ι 25. An amplifier device in accordance with Claim 22 2 wherein said frequency dividing circuit and said threshold signal 3 level circuit are coupled to said filter in parallel to each other. 1 26. An amplifier device in accordance with Claim 22 2 wherein said threshold signal level is variable. 1 27. An amplifier device in accordance with Claim 21 2 wherein said frequency dividing circuit includes an on/off switch. 1 28. An amplifier device in accordance with Claim 21 2 wherein said filter has a cut-off frequency selected to attenuate 3 high frequency noise above 400 hertz. ι 29. An amplifier device in accordance with Claim 21 2 further comprising a volume control circuit coupled to said audio 3 signal source. 1 30. An amplifier device for matching an audio signal from 2 an audio signal source to a pre-determined frequency of a load 3 comprising: 4 an input filter circuit coupled to the audio signal 5 source for developing a filtered signal from said audio signal; 6 a muting circuit coupled to said input filter circuit, 7 said muting circuit having a threshold signal level and only 8 passing the filtered signal at levels above said threshold level; 9 and o a power amplifier coupled to said muting circuit and i said load for amplifying said decoded signal into an amplified 2 signal having a frequency level corresponding to the pre- 3 determined frequency of the load. 1 31 . An amplifier device in accordance with Claim 30 further comprising a decoding circuit coupled to said input filter circuit for selecting between a left and a right audio channel of said filtered signal, developing a decoded signal and applying said decoded signal to said muting circuit. 1 32. An amplifier device in accordance with Claim 30 2 further comprising a frequency dividing circuit coupled to said 3 input filter circuit and said amplifier, said frequency dividing 4 circuit dividing the frequencies of the filtered signal by a pre- 5 determined factor, and developing a frequency divided signal. ι 33. An amplifier device in accordance with Claim 30 2 wherein said threshold signal level is variable. ι 34. An amplifier device in accordance with Claim 30 2 further comprising a volume control circuit coupled to said audio 3 signal source for controlling the volume of the audio signal.

Inventors: SHULTZ LAWRENCE, TUNG DAVID, VINCENT RICHARD, SHULTZ, LAWRENCE, TUNG, DAVID, VINCENT, RICHARD
Applicants: AURA SYSTEMS INC, AURA SYSTEMS, INC.
Application year: 1994
Main classification: H04L29
IPC codes: A63F13, H03G5, H04R5